Human stem cells used to create tiny human livers

Then the researchers transplanted the liver buds into mice, putting them in two places: on the brain and into the abdomen. The brain site allowed them to watch the buds grow. The investigators covered the hole in each animal's skull with transparent plastic, giving them a direct view of the developing liver buds. The buds grew and developed blood supplies, attaching themselves to the blood vessels of the mice.

The abdominal site allowed them to put more buds in - 12 buds in each of two places in the abdomen, compared with one bud in the brain - which let the investigators ask if the liver buds were functioning like human livers. They were. They made human liver proteins and also metabolized drugs that human livers - but not mouse livers - metabolize.

Dr Takebe and his colleagues are now focused on scaling up their process so they can try to take it to the clinic, perhaps to treat babies and children whose livers have failed. He estimated they would need hundreds of thousands of liver buds to replace 30 percent of the liver.